Any point to saving the .opf files?

[stan999]

I don't see any use for them whatsoever. I changed settings to ignore cover and .opf files. I'm convinced these are implemented for a reason, which one would that be?

[yonkyunior]

the metadata changes in calibre was not final until we "save to disk", or convert the file, and any action to send file to another device.
and if calibre database corrupt, then calibre search the opf file first (not sure), then restore the db, since the opf in folder was update than opf inside the epub.

if you open epub file (extract),or open with epub editor, you will see built-in opf file,
you can compare the opf file if you want.

[BetterRed]

@stan999 - yonkunior has the nub of it, here's the unabridged version.

The metadata.opf files in book folders are there to facilitate rebuilding (restoring) of the library database if it gets corrupted somehow (metadata.db in library folder). I've been using calibre for nearly a decade and I never had to rebuild a database.

The metadata.opf file in book folders and the .opf files in epubs have similarities but they are not interchangeable and never will be.

IMO, unless you intend round-tripping Saved to disk formats back into a calibre library there is little point in saving the metadata.opf and/or the cover.jpg files with the saved format files. An exception might be if the format you're saving has no (or limited) embedded metadata - e.g. a MOBI or a CBZ.

The cover.jpgs are where calibre gets the images to display in Book details, Cover carousel and grid, Conversion dialogue, etc. Extracting images from format files or the database would make calibre appreciably slower.

BR

[JSWolf]

Originally Posted by stan999

I don't see any use for them whatsoever. I changed settings to ignore cover and .opf files. I'm convinced these are implemented for a reason, which one would that be?

The reason the cover and the OPF files are there is in case the database gets corrupted. You can restore the database because Calibre gets the information from the OPF files and the cover from the cover files. So if you don't have these files and you need to restore your database, you are not going to be able to and you will have to start over.

So allow Calibre to create the cover and OPF files and be safe. I'm not sure if this will work, but give it a try. Allow Calibre to create the cover and OPF files. Create a new database based on your existing database and copy everything from the existing database to the new database. That (I would think) would create the covers and OPF. If that works and the new database is OK, delete the directory and all the subdirectories in the old database directory.

[BetterRed]

@JSWolf - AFAIK, the covers are not stored within the database - your post seems to be implying they are.

In your second paragraph you refer to something called a 'database' in several places , I presume you mean 'library' - if so why not say so, afaik its not a banned word

BR

[JSWolf]

Originally Posted by BetterRed

@JSWolf - AFAIK, the covers are not stored within the database - your post seems to be implying they are.

In your second paragraph you refer to something called a 'database' in several places , I presume you mean 'library' - if so why not say so, afaik its not a banned word

BR

It is both a library and a database (with external files). But in saying database, I'm meaning the database that can get corrupted and then need to be rebuilt.

As for the cover, yes, I did say that incorrectly.

[BetterRed]

So what tools do you recommend to create new databases, and copy the contents of old databases to new databases etc.

An empty calibre library needs a library folder as a place to store an empty database - in which the baseline database schema is stored. If you add a book, even one with no format files, you'll get an author and a book folder with an opf file.

BR

[stan999]

Yup, I get it now. I'll keep 'em in there even though I usually do an external backup just about every day. This not storing your library in the cloud is really annoying. And forget the server bs thing. I appreciate the input!

[BetterRed]

It is not unknown for people to backup a corrupt database, day after day, after day, after day, after day, after day… until one day…. kaboom! It has been common (best) practice to provide a mechanism to rebuild complex databases from simple raw data since forever

BR

[theducks]

Originally Posted by stan999

Yup, I get it now. I'll keep 'em in there even though I usually do an external backup just about every day. This not storing your library in the cloud is really annoying. And forget the server bs thing. I appreciate the input!

You can keep COPIES in the cloud, just not use them while they are there (with safety. Folk do. Sometimes they get away with it. Sometimes KABLOOEY. Google drive is the only one that I know that damages them unless you first zip the lot before clouding them. )

Content server NONSENSE?
It works.
It makes books available in the existing format (no conversion)
Current release even allows metadata adjustments